Merge symbol values into property values from a bean definition

Springs allows you to externalize property values from a bean definition into a property file. It would be nice if the values of the property placeholders could be read from symbol values. An example:

<bean id="serviceStrategy" class="${custom.strategy.class}"/>

public static void contributeApplicationDefaults(MappedConfiguration<String, String> configuration) {
configuration.add("custom.strategy.class", "com.foo.DefaultStrategy");
}